Cerebrospinal fluid cytology in patients with cancer: minimizing false-negative results.
BACKGROUND
Detection of malignant cells on cytologic examination of the cerebrospinal fluid (CSF) is the diagnostic gold standard for leptomeningeal carcinomatosis. The absence of cells is a primary endpoint for most therapeutic trials. Unfortunately, false-negative results are common. Practical strategies are necessary to remedy this problem.


METHODS
Four physician-dependent variables (CSF sample volume, site of CSF sampling, processing time, and frequency of CSF sampling) were identified, and their contributions to the false-negative rate of CSF cytology were evaluated prospectively in 39 patients with leptomeningeal carcinomatosis. Retrospective data were analyzed to estimate the importance of these variables in daily practice.


RESULTS
False-negative CSF cytology results correlated with small CSF volume (P < 0.001), delayed processing (P < 0.001), not obtaining CSF from a site of symptomatic or radiographically demonstrated disease (P = 0.02), and sampling fewer than two times (P < 0.001). In 1 year, 97% of CSF specimens at the study institution were of inadequate volume; >25% were processed too slowly.


CONCLUSIONS
False-negative CSF cytology results are common, but can be minimized by: 1) withdrawing at least 10.5 mL of CSF for cytologic analysis; 2) processing the CSF specimen immediately; 3) obtaining CSF from a site of known leptomeningeal disease; and 4) repeating this procedure once if the initial cytology is negative.
Glantz
M J
MJ
Department of Medicine, Brown University School of Medicine, Providence, Rhode Island, USA.
Cole
B F
BF
Glantz
L K
LK
Cobb
J
J
Mills
P
P
Lekos
A
A
Walters
B C
BC
Recht
L D
LD
D002555:Cerebrospinal Fluid / Q000166:cytology*; D003581:Cytodiagnosis / Q000379:methods; D005188:False Negative Reactions; D006801:Humans; D008577:Meningeal Neoplasms / Q000473:pathology* / Q000556:secondary; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D013048:Specimen Handling / Q000379:methods; D013129:Spinal Puncture